1. Technical Field
The present disclosure relates generally to orthopedic spine surgery and, in particular, to a minimally open retraction device and methods for its use in a minimally open surgical procedure.
2. Background of Related Art
In recent years minimally open surgical approaches have been applied to orthopedic spine surgery and more recently to spine fusions involving one or more vertebral bodies. Unlike minimally invasive procedures such as arthroscopic knee surgery or gallbladder surgery where the affected area is contained within a small region of the body, spine surgery involving a fusion typically spans a considerably larger length or portion of the body. For this reason, the idea of performing a minimally open procedure on the spine has only recently been approached.
Minimally open surgery offers significant advantages over conventional open surgery. At the onset, the skin incision and subsequent scar are significantly smaller. By using more than one small incision rather than one large incision the need for extensive tissue and muscle retraction is greatly reduced. This leads to significantly less post-operative pain, shorter hospital length-of-stay and a faster recovery overall.
A truly minimally open spine procedure should constitute the smallest damage or disruption possible to the surrounding anatomy. While there may be more than one incision or one long incision, depending on the number of levels needing attention, it is the amount of muscle refraction and scraping that will result in less operative trauma for the patient. A minimally open procedure is also less expensive, reduces hospitalization time, causes less pain and scarring, reduces the incidence of complications, such as surgical site infections, and has an increased speed of recovery.
A typical spine fusion in the lumbar region, whereby at least two vertebral bodies are rigidly connected using screws implanted into the vertebral body and a solid metal rod spanning the distance between said screws, is by its nature not very conducive to a minimally open approach. Furthermore, a spine fusion is typically supported by implanting one or more interbodies into the disc space either using an anterior or posterior approach. An anterior approach requires a separate incision whereby the surgeon accesses the patient's spine through the abdomen. One advantage is the interbody used in this procedure closely matches the footprint of the adjacent vertebral bodies. The disadvantage is that an anterior procedure is typically performed at a different time and requires its own incision and access.
A posterior approach to interbody implantation can be achieved through the same incision as that of the pedicle screws. Implantation of a Posterior Lumbar Interbody Fusion (PLIF) device requires bilateral removal of the facet joint while implantation of a Transforaminal Lumbar Interbody Fusion (TLIF) device can be achieved unilaterally and may require removal of only one facet joint. The advantage of the TLIF is that only one device is implanted into the disc space whereas a PLIF requires two bilateral implants.
While the implantation of pedicle screws can be achieved with relatively little site preparation, interbody implantation requires considerable work. Once the facet joint is removed, the surgeon can begin removing the disc. One or more instruments may be needed to access the site at any time as well as sufficient lighting and suction. To perform these tasks the surgeon needs a suitable opening or channel to work through.
There has been considerable development of retractors and retractor systems for minimally invasive procedures, with most of the new technologies being based on traditional types of surgical retractors for open procedures, predominantly table-mounted devices of various designs. These prior art devices are large and bulky and frequently do not adapt well to a less invasive approach. Standard hand-held surgical retractors are well known in the prior art and can be modified to fit the contours of these smaller incisions, but they require manual manipulation to maintain their position. Typical retractors also are positioned into the soft tissue and levered back to hold the wound open, frequently requiring re-positioning if they dislodge, obstruct the view, or the access ways.
Several minimally open or minimally invasive access devices currently exist to achieve the goal of a suitable working channel. Most are either mounted to the surgical table or held in place by the surgeon or an assistant. Table mounted retractors offer little by way of flexibility. Furthermore, they do not offer a relationship or positional guidance with respect to the patient.
Handheld retractors offer greater flexibility but require an extra hand to maintain position. They also may or may not offer a fixed relationship to the patient but in either case can easily be knocked out of position. Furthermore, handheld retractors typically offer a very long and narrow fixed channel to work through making the procedure even more challenging. Finally, any of the above mentioned retractors typically require a form of dilation to obtain the initial opening. Circular or oblong dilators are well known in the art.